The present invention relates generally to implantable medical devices and, more particularly, to implantable pacemakers and cardioverter-defibrillators for continuously monitoring and accurately measuring atrial arrhythmias.
Implantable cardioverter-defibrillators (ICDs) have been developed that employ detection algorithms capable of recognizing and treating ventricular tachycardias and ventricular fibrillation. Detection algorithms are also being developed to recognize and treat atrial tachycardias and atrial fibrillation. In general, ICDs are designed to treat such tachycardias with antitachycardia pacing and low-energy cardioversion shocks in conjunction with back-up defibrillation therapy. These ICDs monitor the heart rate and the onset of the arrhythmia by sensing endocardial signals and determining when the heart is in need of either cardioversion to treat a given tachycardia or of defibrillation to treat a fibrillation condition.
Certain ICDs have been designed with dual chamber sensing capabilities to detect and analyze both ventricular and atrial endocardial signals. This increase in cardiac signal input to the ICD has provided an opportunity to determine the origin and the nature of atrial and ventricular tachyarrhythmia, and to reduce the frequency of inappropriate therapy being delivered to an implant patient.
However, while the combination of antitachycardia pacing with low and high energy shock delivery, as well as backup bradycardia pacing, in ICDs has expanded the number of clinical situations in which the device may appropriately be employed, improved means of continuously monitoring and accurately measuring atrial and/or ventricular arrhythmia burden is still desired.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading the present specification, there is a need in the art for improved atrial and ventricular monitoring techniques. There exists a further need for such techniques that provide for increased monitoring specificity with respect to various types of atrial and ventricular arrhythmias. The present invention fulfills these and other needs, and provides several advantages over prior monitoring systems and techniques.
The present invention is generally directed to systems and methods for analyzing occurrences of atrial arrhythmias. According to an embodiment of the present invention, occurrences of each of a number of classified atrial arrhythmia rhythms are detected. The classified atrial arrhythmias may, for example, include at least atrial fibrillation and atrial flutter. A duration of time associated with each of the detected atrial arrhythmia rhythms is measured. Trend data is produced with respect to a predetermined period of time using all or selected ones of the measured time durations. The detecting, measuring, and producing processes may also be performed for one or more unclassified atrial arrhythmias.
Trend data may be produced from measured time duration data which has been stored or processed according to a desired format or formats. For example, atrial arrhythmia data may be formatted according to a log format or a time bin format.
Producing the trend data may include summing each of the time durations to produce a cumulative time duration associated with each of the classified atrial arrhythmia rhythms over the predetermined time period. Producing the trend data may also include computing changes in the respective cumulative time durations as a function of time over the predetermined time period.
According to one approach, a percentage of the predetermined time period during which each of the classified atrial arrhythmia rhythms was detected is computed using each of the time durations. Changes in the respective percentages may further be computed as a function of time over the predetermined time period.
The duration or percentage of time a given rhythm was detected during a given atrial arrhythmic episode or series of episodes may be computed using trend data analysis. The duration or percentage of time a given rhythm was detected over the course of a selected snapshot of time can also be computed. Various other types of histogram data may be developed to enhance analyses of atrial arrhythmias experienced by a patient.
In general, the predetermined time period is a selectively programmable period of time or a preestablished time period. For example, the predetermined time period may be selected as a 24 hour time period, a time period based on months or a time period based on years. The predetermined time period may further define a time period between patient analyses, which are typically conducted at a physician""s office or a clinic. The predetermined time period may also represent a time period defined by a life time of a patient. The predetermined time period can also represent a time period defined by a life time of one or more implantable medical devices.
In accordance with another embodiment of the present invention, analyzing occurrences of classified atrial arrhythmias involves detecting occurrences of classified atrial fibrillation (AF) rhythms and detecting occurrences of classified supraventricular tachycardia (SVT) rhythms other than atrial fibrillation rhythms. The classified SVT rhythms may, for example, include atrial flutter rhythms. A duration of time (AF time duration) associated with each of the detected atrial fibrillation rhythms is measured. A duration of time (SVT time duration) associated with each of the detected SVT rhythms is also measured. Trend data is produced with respect to a predetermined period of time using the measured AF and SVT time durations.
Producing the trend data may involve summing the AF time durations to produce a cumulative AF time duration and summing the SVT time durations to produce a cumulative SVT time duration for the predetermined time period. Producing the trend data may further involve computing changes in the cumulative AF time duration as a function of time and computing changes in the cumulative SVT time duration as a function of time over the predetermined time period.
Additional trend data may be produced, such as by computing, using the AF time durations and the SVT time durations, a percentage (AF percentage) of the predetermined time period during which the classified AF rhythms were detected and a percentage (SVT percentage) of the predetermined time period during which the classified SVT rhythms were detected. Changes in the AF and SVT percentages may further be computed as a function of time over the predetermined time period.
According to yet another embodiment, a body implantable system is configured to implement an atrial arrhythmia monitoring methodology of the present invention. The body implantable system may constitute a bradycardia pacemaker, an atrial only device or a dual chamber defibrillator, for example. The body implantable system includes a lead system having at least an atrial electrode. A detector, coupled to the lead system, senses atrial rhythms.
A first timing circuit detects occurrences of classified atrial fibrillation (AF) rhythms and measures a duration of time (AF time duration) associated with each of the detected atrial fibrillation rhythms. A second timing circuit detects occurrences of classified supraventricular tachycardia (SVT) rhythms other than atrial fibrillation rhythms and measures a duration of time (SVT time duration) associated with each of the detected SVT rhythms. A processor, communicatively coupled to the detector and the timer circuit, produces trend data with respect to a predetermined period of time using the measured AF and SVT time durations.
The processor, according to one embodiment, is disposed within the body implantable system or, in accordance with another embodiment, is disposed within a processing system external to the body implantable system, such as within a programmer. According to a further embodiment, the processor is a distributed processor comprising a first processor disposed within the body implantable system and a second processor disposed within a processing system external to the body implantable system.
The processor may produce trend data by summing the AF time durations to produce a cumulative AF time duration for the predetermined time period, and summing the SVT time durations to produce a cumulative SVT time duration for the predetermined time period. The processor may further compute changes in the cumulative AF time duration as a function of time over the predetermined time period, and compute changes in the cumulative SVT time duration as a function of time over the predetermined time period.
The processor may also produce trend data by computing, using the AF time durations, a percentage (AF percentage) of the predetermined time period during which the classified AF rhythms were detected, and by computing, using the SVT time durations, a percentage (SVT percentage) of the predetermined time period during which the classified SVT rhythms were detected. The processor computes changes in the AF percentage as a function of time over the predetermined time period, and computes changes in the SVT percentage as a function of time over the predetermined time period.
The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. Advantages and attainments, together with a more complete understanding of the invention, will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.